Hollow particles have a structure of hollow space and a shell and have properties owing to the structure, such as a low density, a high specific surface area, capability of including a substance, and thermal insulating properties. Among such hollow particles, calcium silicate hollow particles having a shell including calcium silicate are usable as supports typically for drugs, cosmetic components, fertilizers, flavors, and catalysts because calcium silicate is highly chemically stable, harmless to the human body and environment, and inexpensive.
A technique relating to calcium silicate hollow particles having a particle size on the order of micrometers can be found in Patent Literature (PTL) 1.
The technique disclosed in PTL 1 yields hollow porous spherical calcium silicate microparticles having an average particle size of 3.5 μm. The technique enables the spherical calcium silicate microparticles to have a narrower particle size distribution by preparing a water-in-oil (W/O) emulsion and passing the emulsion through a porous membrane.